Some follow up to yesterday's post. Using a Sharkoon HDD Vibe-Fixer in a case which doesn't require screws to install drives doesn't work; the Vibe-Fixer consists of several independent parts which are only loosely coupled. So when the drive starts to work, you'll hear a clatter between the U shaped Vibe-Fixer and the slot in the case.
One solution would be to force some felt between the parts and the slot but it's hard to get there and I'm not sure if the results are worthwhile. So I've bought a ichbinleise® Box HDD 10. This is basically a set of four aluminium pieces held together by four screws which keep the HD between two sheets of damping foam. The whole thing is then glued to the case with a thick foam piece to isolate the vibrations.
I had to use hdparm -M 128 /dev/sda to switch the drive into silent mode, though, to reduce the noise to a low murmur.
The main disadvantage of this setup is heat: I've applied some thermo transfer goo following a tip of the nice guys at ichbinleise.ch. Also, the HD case is in the flow of the front fan. Still the drive reports temperatures between 60°C and 80°C according to smartctl. I hope this is a bug but I'll keep an eye on it.
Another disadvantage is that I can't easily remove the 3.5" drive cage; it's riveted into the case and I'd have to use a drill to get it out. So I glued it in front of the mainboard which means it blocks the lowest two PCI slots. Since I don't need them, it's not a big deal but still ...